Manufacture of cement concrete and apparatus for use therewith



.June 24, 1930.

A. C. KNIFE MANUFACTURE 01-" CEMENT concg'sm AND APPARATUS FOR ussTHERBVIITH Filed Nov. 29. 1926 s sheets-sum i mlmiili'lllllllllllllllllllh:

June 24, 1930. A. c. KNIPE 1,766,911

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IANUFACTURE OF CEMENT CONCRETE AND APPARATUS FOR USE T HEREWITH FiledNov. 29, 1926 5 Sheets-Sheet 3 is v 13 20' Y rfl 26 25 a. a X fi;

Patented June 24, 1930 UNITED stares mm orrics v ARTHUR CYRIL KNIFE, OFWESTMINSTER, LONDON, ENGLAND, ASSIGN'OR IIZO MODERN CONCRETE DEVELOPMENTCOMPANY LIMITED, OF LONDON, ENG-LAND MANUFACTURE OF CEMENT CONCRETE ANDAPPARATUS FOR USE THEREWITH Application filed November 29, 1926, SerialNo.

This invention relates to the manufacture of cement concrete and toapparatus foruse therewitli. y

'111 the manufacture of concrete as generally practised, owing to thethorough mixing of the ingredients which is absolutely neces sary, acomparatively large volume of it'- becomes entrapped in the mass withthe resultthat the concrete when set possesses numerous voids or poreswhich are inimical to the strength of the article or structure produced,even though while mixing, the ingredients have been properly graded.

The object of the present invention is to avoid the consequences of suchan aeration of the concrete and to so mix it that the mass will becomevery dense and therefore stronger and the tendency for it to sweat willbelargely overcome. The invention consists in withdrawing or exhaustingthe entrained air while the ingredients are being mixed in the wetstate.

The invention alternatively consists in mixing the wet ingredients ofcement concrete in a chamber wherein a suitable degree ofsub-atmospheric pressure exists or is maintained. c

The invention also consists in the combination of a cement concretemixing chamber capable of being hermetically closed with a vacuum pumpand a valved connection between the two, a

The invention will now be described with reference to the accompanyingdrawings which illustrate two forms of concrete mix ing machinery towhich the presentinvention has been adapted.

Figures 1 and 2 are respectively a side and end elevation of apaddleetype mixer in which the mixing tank is non-rotating.

Figures 3 and 4 are similar views of a 1'0- tary drum type mixer, and iH Figure 5 is a side elevation of a modified arrangement of the plant.

Referringto Figures 1 and 2, the mixing tank a normally rests upon afoundation plate 6. and is fitted with acover plate 0, a rubber or othersealing gasket (Z being provided between the cover plate and box. Inorder that the box may be hermetically sealed the light 151,560, and inGreat Britain December a, 1925.

iron framework 0 of the machine-carries one end 7 of a toggle leversystem 7 while the other end 7? is pivoted to thecover plate 0. Atraversing screw 9 operated by a hand wheel 9 is used to expand orcontract the toggle levers to either raise and open, or lower and close,the cover plate 0. The mixer shaft 72 passes by means of stuffing glandsis into the interior of the tank and carries the usual'mixing paddles(not shown).

For driving the mixer shaft it a pair of fast and loose pulleys Z arecarried on shaft m which in turn is supported in bearings provided inthe supports a. The shaft 072 carries a sprocket wheel 0 which by meansofa sprocket chain 29 drives another sprocket wheel 9 mounted on asleeve 1" rotating 011 shaft 1 carried by bearings in the same supportsa. On the sleeve r a gear wheel 8 is carried which gears with a wheel tthat is mounted upon one end of the driving shaft it.

By the above gear train a reduction drive upon the mixing shaft issecured and the .mixing tank is free to be tilted about the centre ofshaft 7" to one side in order to discharge the mixed concrete,'.the spurwheel t revolvinglround pinion s to permit this. a: is a hand wheelwhich when operated will, by means of the gears a y and shaft u, operatethe gear 1), w and cause the tank to be tilted about centre r. i

To exhaust air from the mixing tank an air pump 6 ofsuitableconstruction is carried on the same bedplate b and driven by thebelt pulleys Z through multiplying gear wheels 7. The air is exhaustedfrom the tank by'the suction duct 8, separator 9, duct 10 andfiexiblebranch 11, the end of which passes into the tank a through the cover 0.The branch 11 fitted with a vacuum gauge" 12 and a valve 13'to admitatmospheric pressure when opening the tank.

The operation of the machine is as follows After the concrete has beenmixed in the usual way, the cover; plate 0 is forced down upon the. topof the tank by operating the hand wheel y so that the toggle mechanism fis contracted to thus make the jointpaire tight. The stop valve 13 beingthen closed the continued running of the machine will produce asub-atmospheric pressure condition within the tank indicated by thegauge 12 whereby the mass therein will be given greater density and theair spaces or pores left therein will be greatly reduced and minimised.When the treatment is completed the valve 13 is opened and the togglemechanism actuated to lift the cover plate clear of the tank, afterwhich the hand wheel a; is actuated to tilt the tank so that thecontents may be discharged.

If desired, a clutch device generally denoted by 27 may be arranged onthe power shaft so that the mixer may be operated independently of theair pump or both may operate together. Such clutch is operable by meansof lever 28 as shown.

Referring now to Figures 3 and 4, the rotary drum mixer is is drivencircumferentially by any suitable power unit, and the wheels 15 supportthe drum on a suitable foundation 16 upon which is erected a lightframework 17 for the parts of the machine. 1 ach side of the drum has anopening for feeding and discharging the drum adapted to be closed by acircular cover plate 18 adapted to be sealed hermetically as before.Each door is centrally fitted with a trunnion piece 19, having a centralbore extending. therethrough. and to support each door a radial arm 20is provided. One end of such arm engages its corresponding trunnionpiece 19 by means of a suitable ball bearing not shown,. while the otherend is hinged upon a vertical pin 21 supported by a small bracketsecured to the machine framework 17. The upper end of the vertical hingepin carries a worm wheel indicated at 22 in gear with a worm 23. Bothworms are fitted upon a shaft 23 extending from one side of the drum tothe other and are operated by the hand wheel 24. The two worms arerightand left-hand respectively and the arrangement is such that byturning the'hand wheel both of the cover plates 18 are simultaneouslyactuated to cover or uncover the respective openings in the sides of thedrum.

A flexiblepipe 25 and 26 is connected respectively to the outer ends ofthe trunnion pieces 19, one pipe being the vacuum pipe and the otherbeing in communication with a water supply to feed water into the drum.

The arrangement of the air pump separatorand other details may be thesame as that describedin the first modification but are not heredescribed.

From the foregoing it will be understood that both cover plates may behermetically closed upon the drum openings by the worm gear and willrevolve with the drum in their ball bearings in the ends of the radialarms. When de-aeration is accomplished, both cover plates may be swungopen clear of the usual feed or discharge mechanism.

To efiect a quick release of the doors a suitable clutch devicegenerally indicated at 29 under the control of hand lever 30 may becombined with the hinge pins 21 so that the doors may be swung clear byhand out of the way of the feed or discharge mechanism.

It is to be understood that if necessary the concrete may be de-aeratedin a chamber separate from the usual mixing chamber and an example ofsuch an arrangement is shown in Figure 5.

According to this a rotary drum mixer 31 is driven by an electric motor32 through suitable gearing such as the spur wheels 33, the mixedconcrete being discharged through the inclined chute 34, this being allaccording to standard practice. A further chute 35 supported on abracket 36 pivoted at 37 conducts the material. from chute 34 to theseparate de-aerating chamber 38, the chute 35 being adapted to be swungaround the pivot 37 away from the chamber 38 so as to allow the cover 39to be fitted on to the deaerating chamber 38. Such cover is raised andlowered by the toggle linkage system i1 as already described withreference to Figures 3 and a. To actuate the de-aerator an electricmotor a2 is provided which by means of a worm gear box 43 and gearing a9 ist and ie drives a shaft f6 that passes into the de-aerator chamber38. Such shaft carries suitable agitating devices not shown toenergetically stir up the concrete. The electric motor 42 also drives bymeans of a clutch 47 an air pump 48. i

The mixer 31 having discharged the mixture into the de-aerator chamber38, the chute 35 is swung out and the cover 39 lowered and tightlyclosed by means of the toggle links. The clutch a7 is then put into gearto drive the air pump 48, which by means of duct 49 in dotted lineswithdraws air from the de-aerating chamber. Suitable means are providedfor tilting the deaerator or otherwise removingthe concrete thustreated. 50 shows a hand brake for controlling the speed of theagitator.

In a large plant several mixers may be served by a single air exhaustingmeans and moreover with reference to Figures 3 and 4 suitable devicesare provided to maintain the centres of the cover plates in line withthe drum axis. t

From the foregoing it will be understood that the cement concretemanufactured in the manner described will be very dense in structure andtherefore stronger which is of particular value-when the concrete is tobe exposed to weather action or is subjected to abrasion such as onconcrete roads Where both are present. 8 v

Another characteristic of such de-aerated concrete is that owing tothe'absence of pores its liability to sweat is largely minimized.

Having now described my invention what I claim as new and desire tosecure by Letters Patent is 1. The method'of producing densified,deaerated cement concrete consisting in mixing the ingredients in avessel open to the air until a homogeneous mass isobtained thensubmitting the mass to agitation in a way to bring all portions thereofto the uppersurface of the mass and While being agi tated subjecting thesurface of the mass to'a high vacuum until the air is extracted andafter the air is extracted working the mate: rial under normalatmospheric conditions.

2. A cement concrete machine comprising a concrete mixing container,means to agitate the concrete in the container, means for admittingwater to the concrete constituents, an exhaust pump to withdraw air fromthe concrete, said pump being operable whilst the concrete is beingmixed,a clutch operable for connecting the agitating means or pump orboth to a source of power, a cover plate on the container, operatingmechanism for closing the cover plate air tight, a separator and apartially flexible pipe connectionarranged in series between the airexhaust pump and the container, and a tWo Way valve on said'pipeconnection operative to allow either air to be exhausted from thecontainer or to establish atmospheric pressure therein.

In testimony whereof I have signed my name to this specification.

ARTHUR CYRIL KNIFE.

